Tgp chi Khoa hoc Truong Dgi hpc Cdn Tha Phgn B: Nong nghiep, Thuy sdn va Cdng nghi Sinh hpc: 34(2014): 28-35
Tap chl' Khoa hpc Tru'dng Bai hpc Can Thcf website: sj. ctu. edu. vn
A HOC
HIEU QUA TIEU DIET BAO Tif Bacillus subtilis DANG HUYEN PHtl VA DANG KHO BANG XUNG ANH SANG
Nguyen Bao Lgc', Nicorescu Irina^ va Orange Nicole"
' Khoa Ndng nghiep & Sinh hgc (Ing dung, Tneang Dgi hgc Can Tha
'LMSM. University of Rouen, EA 4312. 55, rue Saint-Germain, 27000. Evreux, France Thdng tin chung:
Ngdy nhgn: 22/04/2014 Ngdy chdp nhgn: 30/10/2014 TUle:
Pulsed light efficacy on the decontamination of bacillus subtilis spores in liquid and dry state
Tirkhda:
Xung dnh sdng, gia vi. khd nhiem. bdo tie B. subtilis xung dnh sdng, gia vi, khu nhiim.
bdo lie B. subtilis Keywords Pulsed light, spices, decontamination. Bacillus subtilis7spore^
ABSTRACT
In this work, pulsed light (PL) efficacy was investigated on B. subtilis spores in liquid and dry state (glass marbles and spices). We stiuiied the bacterial suspension in conditions (0.6 J.cm'^/flash) and spices at 1 J.cm'^/flash. In liquid state, only 0.9 log microbial reduction was recorded when 6 J.cm'^was applied. SEM analysis showed that B. subtilis spores in suspension were not affected by the PL treatment. When DNA extracted fi'om B. subtilis spores was analyzed, no significant difference was found
between the control and PL-treated samples. In dry state the destruction level remained below 1 log when a treatment of 10 J.cm'^ was carried out on black pepper and ground caraway, while a 2.8 log microbial reduction was reached for glass marbles When control and PL-treated B subtilis spores in dry slate were investigated by SEM, no disruption in spore structure was recorded but a significant number of PL-treated spores were flattened.
TOM TAT
Trong nghien ciru ndy. hieu qud diet kliudn cita xung dnh sdng dugc ddnh gid tren bdo tie Bacillus subtilis dgng huyen phii vd dgng khd (bdo tie vi khudn dugc gdy nhiim tren bi thuy tinh vd gia vi). Nghiin cuu dugc thtfc hiin vdi cudng dg 0,6 J.cm'^/xung tren huyen phii vi sinh vgt, vd tren gia vi vdi cudng dg 1 J.cm'^/xung. O dgng hi^en phii, vdi cucmg dg 6 J.cm'^ chi tieu diet dugc 0,9 log bdo tie vi khudn. Hinh dnh phdn tich bdng kinh hien vi dien tie (SEM) cho thdy bdo tie B. subtilis d dgng huyen phii khdng bi dnh hudng bdi xie ly xung dnh sdng. Qua phdn tich ADN trich ly tie bdo tu B. subtilis. khdng nhdn thdy su khdc biet y nghTa giUa mdu xie ly vd mdu ddi chung. O dgng khd. muc do tiiu diet bdo tii: B. subtilis dgt dugc dudi 1 log khi xir ly d cudng dg 10 J.cm'^ tren hgt lieu vd tieu hdi, trong khi tren bi thuy tinh thi muc dg nay dgt tdi 2,8 log. Khi phdn tich hinh dnh bdo tie B. subtilis dgng khd cua mdu ddi chung vd mdu xie ly bang xung dnh sdng qua kinh hien vi dien tu, cdc bdo tie deu khong bi phd vd bdi xung dnh sdng, tuy nhien cd mgt sd luang ddng ke bdo tu bi thcry ddi hinh dgng dugc phdt hiin trong mdu da xu ly bang xung dnh sdng.
Tgp chi Khoa hpc Trudng Dgi hgc Can Tha
1 GlOfI T H I E U
Xung dnh sdng Id mdt ky thuat xiir ly khdng dimg nhiit vdi kha ndng xuyin thdu rdt tiidp,_dan|
dugc ling dung rdt nhilu trong viic khii nhiim bi mat. Phuong phap nay sd dung den xenon phat ra dnh sang trdng (cd budc sdng ttong khoang 200 nm - 1100 nm) vdi cudng dp cao (Wekhof, 2000). Khd ndng khu nhilm cua phuong p h ^ nay chu ylu la do tia cue tim (200 nm - 400 nm), tao nin su huy hom ADN cda tl bao vi sinh vat. Bin cgnh do ciing cd mdt sd ca chl khdc dugc de cgp den, vi du nhu su pha vd mang tl bao vd kha nang lam tang kich tiiudc khdng bdo da dugc nghien cuu trin te bdo ndm men (Takeshita et al., 2003).
Xung dnh sang da dugc nghiin ciiu va iing dung rpng rdi ttin cac vat liiu Iam bao gdi (Dunn et al, 1995; Turtol and Nicolau, 2007, Levy et al, 2011, 2012), cdc thilt bj dung Uong cdng nghiip (Ozen and Floros, 2001; Rajkovic et al, 2010) va tren thgc phdm (Gomez-Lopez et ai, 2005; Ozer and Demirci, 2006; Sharma and Demirci, 2003;
Ramos-Villarroel et ai, 2012; Palgan et ai, 2011).
Dd cd nhieu nghiin cihi vi hiiu qua lac dpng cua xung dnh sdng Uen te bao vi khuan (Feuilloley et al, 2006; Massier et al, 2011; Fariell et al, 2011; Nicorescu et al, 2013). Tuy nhiin, chi co mdt vai nghien ciiu (Fine and Gervais, 2005; Levy et al, 2011; 2012) danh gid khd nSng tiiu diet bao tii ciia xung dnh sang tiong ITnh vuc an toan thuc pham.
Mpt ttong nhOng loai bdo tii vi khudn thudng gdp nhat trong cdc Ioai gia vi Id bao tu cda B.
subtilis, vdi miic dp nhiem thudng xuyin len tdi 8 log cfu/g (McKee, 1995; Keitii, 1998). Day la loai vi khudn gdy mpt so loai ngp dpc thuc phdm, cd thl ke din nhu 6i mua, tiiu chay, dau bung. Hdu hit cdc bao cdo dua ra deu liin quan den viec tieu thu mayonnaise, hanh ngam, rau ddu ddng hop (Kramer and Gilbert, 1989). Kha ndng chdng chiu cua bdo tii B. subtilis trong qud trinh chl biln thuc phdm la rit tot, dilu nay cd thi giiip chung tdn tai sau ojua trinh thanh triing. Thuc su, di lie chl bao td vi khudn bdng nhiit, tia cue dm, cac logi chieu xg va xung anh sdng thi cdn phdi sii dyng cudng do cao hon so vdi tl bdo sinh dudng (Farkas, 2007).
Han n&a, bao tii' nam moc, vi dy nhu bao tii A. niger, dugc bilt vdi khd ndng ching chm r4t tit vdi tia cgc tim. Nghien ciiu nay dugc thgc hien vdi muc dich so sdnh hi^u qud khu khudn ciia xung dnh sdng ttin bdo tCr B. subtilis dang huyin phii va dang khd (gay nhilm Uin bi thuy tinh va gia vi).
Phdn B. Ndng nghifp, Thiy sdn vd Cong nghi Sinh hpc- 34 (2014): 28-35 '
2 PHU^ONG PHAP NGHIEN ClltJ 2.1 Chung vikhuSn
Bao tii B. subtilis (ATCC 31 324, DSMZ 704, Braimschweig, Diic) cung cdp bdi INRA Dijon, dugc pha loang ttong mdi tnrdng peptone (PS) (Biokar Diagnostics, Phdp) din ndng dp 10^ bao tii/mL. 10 mL dung djch viia pha lodng dugc xii ly bdng xung anh sdng (dugc md id ttong myc 2.3).
Mpt don vi log bao tii vi khudn la logarit ciia mat so bao tii vi khudn (cfii/mL hoac cfii/g).
2.2 PhuoTig phap gfiy nhilm nhfin tao gia vj vd bi thuy tinh vdi bao tii B. subtilis
Bi thuy tinh (dudng kinh 4 mm), hat tiiu den va tilu hdi dugc gay nhilm vdi dung dich bdo tu B.
subtilis (dugc md ta ttong muc 2.1). Mlu dugc say khd ttong diiu kien vd trimg d nhiet dd phdng trong tiidi gian 15 gid, tilp theo, mau dugc xii ly bdng xung anh sdng (dugc md ta ttong muc 2.3).
Mlu xii Iy va ddi chiing dugc hoa tan trong m6i trudng PS va khudy ttdn trong tiidi gian 2 phiit.
Phuong phap pha loang theo ddy tii^p phan dugc sir dung dl cdy Uang ttin bi mat mdi trucn^
Columbia-agar (AES, Phap). Phuang phdp dim khudn lgc (cfii) dugc tiiuc hien di ddnh gid khS nang sing sdt cua bdo tti S. subtilis sau khi xii ly vdi ximg dnh sang so vdi mlu ddi chiing.
2.3 Phuong phap xu 1;^ xung anh sdng Thilt bi xu ly xung anh sang dugc cung cap bM Claranor (Phap) gdm cd I bd phdn ti'ch dien va I budng xii Iy, ttong dd cd 4 den xenon dgng hinh tru (Massier et ai, 2011). Thilt bj tiu nghidm ndy tgo ra mpt loat cac xung anh sang cd budc sdng tir 200 din 1100 nm vd thdi gian ciia mdi xung Id 300 jis.
Trong till nghiim nay, cudng dp nang lugng si dung dl xu Iy huyin phii bao tii Id 0,6 J.cm'^/xung va gia vi Id 1 J.cm'Vxung.
Huyen phu ciia bdo tii B. subtilis dugc dgi^
ttong mdt hop hinh chii nhdt bdng thach anh va dugc xCc I^ o 3000 V, 1 Hz voi 1, 2, 4, 6, 8, 10 xung cd cdu hirih 4 den va nang lugng sii dyng la 0,6 J.cm"^/xung. Trudng hgp cua gia vj vd bi thuj tinh dugc gdy nhiim nhdn tgo vdi bdo tii B. subtilis, thi mlu dugc xii I;^ Uong diiu kiin ddo gpn d 3000 V, 1 Hz vd 10 xung vdi cung thilt bi ' nhu tren nhung cd cdu hinh 3 den dk dat dugc cudng dp nang Iugng Id 1 J.cm"^/xung. Sau Idii dirge xu ly, fhi mau dii chung vd mlu dugc xii 1^
si dugc phdn g'ch ngay ldp tiic. Thi nghiem dugc thgc hiin 3 ldn ldp lgi.
Tgp chi Khoa hgc Trudng Dgi hgc Cdn Tha Pftan B: Ndng nghiip, Ihiiy sdn vd Cong nghi Sinh hpc: 34(2014): 28-35 2.4 Phutrag pbap trich ly ADN cQa bao tu
B. subtilis
ADN ciia bdo tu B. subtilis dugc trich Iy dua theo phuong phdp cda Rieserunan and Nicholson (2000) vdi mpt s6 thay doi. 0,02 g bOt bdo tu (khoang 10'° bdo tu/g) dugc cho vdo dng eppendorf cung vdi 2 mL dung dich SE (50 mM ttis base [pH 10], 8 M urea, 50 mM ditiiiotiueitol, 1% SDS) va dugc u d 60°C ttong tiidi gian 90 phut Tilp tbeo la giai doan xii Iy sdc nhiit (3 Idn) liin tilp tu - SO-'C rdi 100''C vd tilp tiieo dung djch dugc ly tdm d 7000g ttong thdi gian 10 phiit d 20°C de thu dugc phdn can tl bdo. Phdn c3n t l bao nay tilp theo dugc riia 3 lan vdi dung dich STE (pH 8) (10 mM tiis HCI, 1 mM EDTA, i50 mM NaCI). Giai dogn thuy phan bdng enzyme dugc thgc hiin bang each bd sung thim dung dich dim PI (10 mM tiis base [pH 8], 2 mM EDTA, RNAse I IOO pg.mL"') vd lysozyme (10 mg/mL), sau dd mlu dugc u d 37''C. Sau 1 gid u, mlu dugc thim vdo 100 pL SDS 10% va ttdn ddo ngugc nhiiu Idn (den khi hSn hgp trd nen md due). Sau dd h§n hgp dugc nia vdi 625 pL dung djch phenol-chloroform vd Iy lam d 13000g, 20°C Uong tiicri gian 10 phut.
Tiip theo h6n hgp dugc thim vdo 625 pL phenol bao hoa va Iy tam d 13000g, 20''C ttong tiidi gian 10 phiit Cac budc tiep theo ciia phuong phdp trich ly va ddnh gid ADN bao tii vi khuan gidng vdi phuang phdp trich ly vd ddnh gid ADN cua tl bao sinh duong vi sinh vdt dugc viit bdi Nicorescu et al (2013).
3 KET QUA VA THAO LUAN 3.1 Tac d^ng ciia sung anh sang den bao tiir B. subtilis dang huyin phii
Trong thi nghiem ndy, viic ddnh gid hiiu qud cOa xung anh sdng dugc thuc hien Uin huyen phu
cua bao tii B. subtilis a ndng dp 10* bao tii/mL vd ket qua dugc thi hien tten Hinh 1. Kit qua cho thay d dilu kien xii IJ 6 J.cm"^, miic dp tieu diit bao tii chi dat dugc 0,9 log, diiu nay khdng dinh kha nang chiu dung rat tdt ciia bdo tii so vdi ti bao sinh dudng (Nicorescu et al, 2013). Kha ndng khur nhiem thap cua phuong phap nay cd thi dugc giai thich bdi miic dp day dac cua bao Hi gong huyin phu (10* bao tii/mL) va cung do cudng dd ndng Iugng su dung thdp (6 J.cm"-). Miic do day dac cua bdo tu gong huyin phu dnh hudng quan ttgng den hiiu qua khir nhiem ciia xung dnh sang, la do: i) cdc bdo tii nay cd thi hdp thu mdt phdn cac budc sdng cd khd nang diet khuan ciia phd xur^ ndng (Levy et ai, 2011), va ii) cac bao hi nay cd the tao ra tac dyng cbe khudt (EInmasser et ai, 2007).
Theo nghien ciiu ciia Bushnell et ai (1998);
Wekhof (2003), hieu qua khii nhiim cda xung anh sang Uin bao Hi B. subtilis ttong nude mudi phu thudc rat nhiiu vdo cudng do nang lugng sur dyng.
Thai vay, miic do tieu diet bao Hi dat dugc khi xii Iy 1 xung Id 2,5 va 6 log vdi miic dd nang luong sii dyng tuong iing la 600 J vd 1200 J. Vdi kit qud tuang tu, Sonenshein (2003) nghien ciiu tac dung khu nhiem ciia xung anh sang vdi miic dp ndng lupng xu dyng Id 15,8 J.cm"^/xung trin bao tii B.
subtilis ttong mdi ttudng nude dd khii ion va vdi 3 xung thi miic dp tieu diet bao tu dat dugc la 6 log.
Mdt sd nghiin ciiu khac cho thdy viic tieu di^t toan bd (6 - 8 log) bao tii B. subtilis, B. pumilus dat dugc khi xOr ly 1 - 3 xung vdi cung miic dp nang Iugng nhu ttin (Bmhnell et al, 1998). Mdt cdch tdng quat, di tiiu diet bdo tii thi phdi can mgt mii'c dd nang lugng cao hon so vdi viec tieu diet t l bao sinh dudng. Tuy vdy, xung anh sang vdn cd the dugc sir dyng mdt each hiiu qud ttong viic tiiu diet baotii^ tf^E^iat-tliy'crpham (Anderson et al, 2000; June/a/., 2003).
Tpp chi Khoa hoc Tmdng Dgi hgc Cdn Tha Phdn B: Nong nghiip, Thuy sd*j va Cong nghi Sinh hpc: 34 (2014): S-iJ*
0 1 2 4 6 8
Sd Iugng xung anh sang
Hinh 1: Tac d^ng khir khufin ciia xung anh sdng trin huyin phii bao tu B. subtilis Ket qud ttin dugc bd sung bdng thi nghiem
phdn tich hinh anh ben ngoat ciia bdo tii B. subtilis.
Hinh SEM (Hinh 2a va 2b) cho tiidy bao tii B. subtilis khdng bi phd huy bdi xung anh sang.
Kit qua nay khdng ddng nhat voi ket qud ciia Wekhof (2001) dua ra. That vdy, nghien ciru cua Wekhof (2001) cho thay cd sg phd buy bao tu B.
subtilis khi xu Iy bang xung dnh sang ttong mdi
trudng khd (trang mdng trin PET hoac ttin mgt kinh thuy tinh). Tuy nhiin, Pham vi nghiin ciiu nay dugc thgc hien tten huyin phii vi sinh vdt, diiu dd cd thi din din viic bao td khdng bi pha huj bm xung anh sang. Setiow and Setlow (1998) da chi ra rdng, ca chi tieu diet bao tii khdc nhau dang kl khi xii ly Uong mdi irudng ran vd mdi tmdng Idng.
a-'B,.-rf«fcrf^&^n(k Hinh 2: Hmh SEM cua bao tir B. subtilis
a) mau doi chihig; b) mfiu xu IJ 6 J.cm-^ (3000 V, 1 Hz, 10 xung)
TQP chi Khoa hgc Trudng Dgi hgc Cdn Tha Phin B: Ndng nghiip. Thiiy sdn vd Cdng nghi Sinh hpc: 34 (2014): 28-35 Tiip theo, thi nghiim kiim ua khd ndng pha
huy ADN cua bdo tii B. subtilis bdi ximg anh sang dugc thuc hien. Hinh 3 cho tiidy khdng cd su khac biet dang ki giita mdu ddi chiing vd mlu xii !y bdng xung dnh sdng.
triic va kha ndng chju dgng tdt cua b ^ Hi. Han nua, ADN cua bdo Hi vi khudn cd hinh dang khac hon so vdi ADN cua te bao sinh dudng. Theo Setlow and Setiow (1987) bao Hi B. subtilis khdng tgo ra bat ky lien ket nhi hgp nao cua pyrimidine.
Nhiing gia thuyit gan day lien quan den viic lie che bao tii bang tia cue tim cho rang chiic ndng ciia AND bi gidn dogn la do lien kit ngang va/hodc vd sgi ADN (Harm, 1980). Ngoai ra, Riesenman and Nicholson (2000) khang dinh rdng, mang protem ddy ciia bao Hi B subtilis ciing tgo cho no kha nang chdng chju tdt vdi cac diiu kiin ben ngodi. Chinh vi thi, theo nhieu tac gid, kha nang chiu dung cao cua bao Hi vi khudn vdi tia cgc ti'm, dac biet la d ttgng thai khd (Gardner and Shama, 1998) se hgn che kha nang khu nhiim cua xung dnh sdng, do dd ma viic chi sii dung xung anh sang se khdng du manh dk dam bdo khd trimg hoan loan.
3.2 Hiiu qua khu nhiem ciia xung anh sdng tren bi thuy tinh vd gia vi dfi dugc gfiy nhiem vdi bdo tir^. subtilis
Trong thi nghiem nay, hiiu qua ciia xung dnh sang dugc nghiin cuu ttin mlu dgng khd (bi thuy tinh va gia vi) da dugc gdy nhiem vdi bdo Hi B. subtilis. Kit qua thi nghigm cho thay viec xii ly tten bi thuj tinh thi xung dnh sdng cho hieu qud khd nhilm cao hon so vdi viic xii ly tren hat tiiu vd tiiu hdi (Bang 1). That v^y, ket qua ttong Bang 1 cho thay, miic dp tiiu diet bdo tii chi dgt dudi 1 log khi sir ly 10 J.cm"^ tten hat tieu den va tilu hdi, ttong khi ttin bi ihuy tinh thi miic dp nay dgt 2,8 log. Vdi nghien ciiu tac dung khii khudn cua tia hdng ngogi tten bpt dt gay nhiem vdi bao Hi B. cereus, Staack et al (2008) ciing cho thdy tac dyng thap ciia phuang phdp nay (khd nang khii khuin dgt cao nhdt Id 1 log). Theo tac gia, nguyin nhan la do bdt dt cd dp boat dgng ciia nude aw thip (0,8), dieu nay lam tang kha nang chiu nhiit cua bao tii. Kit qua thi nghiem phii hgp vdi nghien ciiu Irudfc do cua Jun et al (2003). Thdt vdy, khi xii \}f bpt ngd da dugc gay nhiim vdi bao Hi Aspergillus niger bdng xung anh sang d cudng dp 2900 V va khoang cdch 8 cm, thi hi^u qud khur nhiem dgt dugc la 1,3 log.
Bang 1: Ket qud xijr If xung anh sang tren bi thuy tinh va gia vi da dugc gfiy nhiim vdi bao tir B. subtilis
Hinh 3: Anh hudng cua xung anh sdng lin ADN cua bdo tu* B. subtilis M: chudn; X: xung
Theo cac tai lieu tham khao, khd ndng diet kliudn cua tia cue ti'm chu yeu la do tac dung quang hoa, gay ra sg thay ddi ttong can tnic ADN (chu yiu la cac pyrimidine) ciia vi khuan, vi nit va cac tdc nhan gdy binh kliac sang dang liin kit nlii hgp (Mitchell et al, 1992). Sg hinh thanh cac cau ndi nay si ngan chgn giai dogn giai nen cda phan Hi ADN trong qud ttinh nhdn ban vd vi thi, vi sinh vdt si mat kha ndng sinh sdn. Niu khdng cd ca chi sua chita thich hgp, thi kit qua se dan tdi su dot bien, sg phien ma vd nhdn ban gen bi suy giam va cudi cimg din den su tiiu diit sinh vgl (McDonald et al, 2000). Mdt vdi nghiin ciiu cho rdng su khac nhau giua co che tiiu diit bdo Hi vLkhuan va te bao sinh dudng chd ylu la do sg khac nhau ttong cdu
M§u Bi fliuy tinli Hat tieu den Tilu hdi
Mih: d$ giam tbeo sd thfip phan (log) sau khi xu ly d cudng dg 10 J.cm'^
2,8 ±0,1 0,8 ± 0,03 0,9 ± 0,04
Tgp cbi Khoa hpc Trudng Dgi hpc Cdn Tha Phdn B: Nong nghiip. Thuy sdn vd Cong nghi Sinh hpc: 34 (2014): 28-35 Hiiu qua khu khudn tiidp ban ttong tiirdng hgp
ciia lieu va tilu hdi so voi bi tiiuy tinh (Bdng 1), cd thl duoc giai tiiich bdi be mat khdng ddng nhat cua hai Ioai gia vi nay. That vay, ttong tiirdng hgp ciia bai logi gia vi, bao Hi khdng chi bam ttin bi mat cua hgt, ma chiing cdn cd till dn ndp d nhung vi tti 16m cua hgt, lam cho vi sinh vdt cd tiie it ho|c kliing chiu tdc ddng khu khudn cua anh sang, dieu d6 lam hgn chl hieu qua khii khudn ciia phuang phdp nay (Fine and Gervais, 2005). Lagunas-Solar et al, (2006) cung da dua ra mdt gia tiiuyit tirong tu, cdc tdc ^d nay cho rdng vi sinh vat cd the dn nip irong cdc dudng nut tten bl mat thgc phdm hogc cd Ihi tiiam nhap vdo dudi ldp bieu bi san
phdm, diiu dd Idm gidm hiiu qua khd nhiim ciia phuong phap nay va nd ddi hdi phai su dui^
mdt muc do nai^ lugi^cao hon. Hon nita, bdo tCr cd kha ndng chdi^ chiu vdi tia cgc tim cao hon nhilu so vdi t i bao sinh du&ng, ddc bi|t la trong dilu kien dd dm itAp va do dd rat khd de tieu diet chiing.
Tilp theo, hieu qud khil khudn cua xung dnh sdng ttin bao td B. subtilis dugc danh gia bdng hinh SEM. Hinh 4b cho tiily mlu xii \f bdng xung dnh sang, bao tti khdng bj phd buj, nhung cd m§t sd ddng ki bi biin dang dudi tac dyng cua phirong phap nay.
a) Mau ddi chiing
Hinh 4: Hinh SEM ciia hat tiiu hdi Kit qua thi nghiim ndy phii hgp vdi nghiin cdu ciia Wekhof (2001), bao lii B. subtilis a ttgng tiidi khd (trdi trin ldp nhga PET hogc ttin ldp kinh thuy tinh) dugc xu IJ bdng xung anh sdng (7 J.cm'^) va kit qud la bao tii hodn lodn bi biin dgng nhung khdng xuit hi?n vit vo hodc mil nao. Khi so sanh tdc dyng ciia xung anh sang ttin te bdo sinh dudng (Nicorescu et al ,2013) vd bao tu: B. subtilis (Hinh 4b), nh|n thdy rdng bdo lii il bj tdc ddng hon rat rihilu so vdi ti bao smh duong. Dieu ndy cd the dugc giai thich b ^ g 2 gia thuyit sau: i) bao tu cd kich thudc nhd ban nhieu so vdi ti bdo sinh duSng, dilu ndy Idm cho chiing de dang an nap ttong cac vit mit hodc d giiia nhitng hat gia vi (Elmnasser et ai, 2007) vd ii) vdi kich thudc nhd be ciia bao Hi, si ldm cho vi?c hap thu tia cgc tim cua chung giam di, dieu ndy si lam hgn che hieu qua khii nhilm cua phucmg phdp ndy. Wekhof (2001) cho rai^
hi^u qud khii khudn cua xung dnh sdng cung phu thupc vdo kich thudc cua ti bdo vi sinh vdt
4 KET LUAN
Thi nghiim nay dugc thuc hi^n nhdm muc dich so sdnh higu qud khu khudn cua xung anh sang ttin
b) Mlu x& ly bling sung Anb sing if 10 J.cffl-^ , (3000 V, 1 Hz, 10 xung)
dugc gay nhilm vdi bao tur B. subtilis .' bdo tit B. subtilis dang huyin phii va dang khd (bdo,;;!
Hi dugc gdy nhiim tten bi thuy tinh va ^ vi). Ket ^ qua nghiin ciiu da cho thdy, ddi vdi bdo tii dgngf^
huyin phu, xung dnh sang chi giam dugc 0,9 log so vdi si lugng ban ddu. Tuy nhiin, qua quan sat ti"6ii hinli SEM, bao tti d dang huyin phii khdng bi phd^
liuj bdi xungahh'sang. Khi pfidiTtfch ADN, thl ket"' qud ciing cho thdy phuang phdp xur IJ niiy khflng anh hudng din ADN cua bao Hi. Ddnh gia hi?u qud khii khuan cua xung dnb sdng ttin bi thuj tinh vd gia vj da dugc gay nhiem vdi bao tii B. subtilis.
Mirc dp diit khuan dgt dugc dudi 1 log khi xii IJ tten mau gia vi, ttong khi mlu bi thuy tinh thi ket qud dgt dugc la 2,8 log. Qua phdn tich hinh dnh bao tii ciia mau ddi chung va mlu xii ly bdng xung dnh sang, khdng cd su phd huj ti bao nao dupe phat hi?n, nhung cd mdt sd ddng kl bao tii bi thay dii hinh dang sau khi xii IJ bdng xung anh sdng.
Nghiin ciiu nay cho thdy: (I) rit khd di dgt dugc miic dp tiiu diet Idn hom 1 log ddi vdi bao tir B. subtilis dang huyin phii hoac dang khd (gdy nhiim ttin gia vi) va (2) cdu tnic bl mat ciia thuc pham dnh hudng quan ttpng din hi?u qua di^t khudn ciia xung dnh sdng, diiu dd khdng dinh dl
Tgp chi Khoa hpc Trudng Dgi hgc Cdn Tha Phan B: Nong nghiip, Thdy si h Cong nghi Sinh hpc: 34 (2014): 28-35 tiiu diit vi sinh viit ttin thgc phdm dang bdt thi cln
CO 1 phuang phdp du mgnh hoac kit hgp nhilu phuong phdp vdi nhau.
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